The present invention relates to a nozzle apparatus and method for dispensing powder coating material from a container such as a cardboard shipping box.
Manufactured objects are commonly coated by spraying an electrically charged powder onto the object while the object is electrically grounded. Electrostatic attraction holds the powder on the object until heat is applied to flow the powder together and to cure it. An apparatus for electrostatic powder coating typically includes a powder coating material storage container, a container for holding and suspending powder in a fluid such as air, a jet pump for conveying fluidized powder, and a spray gun. Using additional fluid, the jet pump induces a stream of fluidized powder from the container and propels the fluidized powder through a hose leading to the spray gun. The powder particles are electrically charged via electrodes at the nozzle of the gun and sprayed onto the object to be coated.
However, various difficulties arise in dispensing the powder coating material from the storage container so that a steady, consistent flow of fluidized powder is supplied to the spray gun. Conventionally, the powder coating material is shipped to a powder coating facility in a plastic bag in a cardboard box. Each box may carry up to 300 pounds or more of powder coating material, for example, but a 45 pound box is more common. Alternatively, a metal shipping drum may be used. In either case, the powder coating facility operator would normally transfer the powder coating material from the shipping container to a large feed hopper, where it could then be pumped to the spray gun.
However, when it is desired to use different powder coating colors, it is necessary for the operator to either purchase a different hopper for each different color, or to transfer the powder coating material back to the shipping container or other temporary storage container so that the hopper can be used with a different color. However, this is unsatisfactory since it is expensive and inconvenient for the operator to purchase and store a number of separate hoppers. Additionally, the hopper must be thoroughly cleaned to prevent contamination when a different color is used.
Moreover, once the shipping container is opened, the powder coating material is subject to contamination from a variety of factors, including atmospheric conditions such as moisture, dirt from the facility, and lint or hair from the operator or his clothing. Additionally, various health risks may be posed to the operator with exposure to the powder coating material due to airborne epoxy, vinyl, polytetrafluorethylene (Teflon), acrylic, polyester, and/or urethane components, and other substances which may be released.
Accordingly, the desirability of dispensing the powder coating material directly from the shipping container has been acknowledged. For example, one system for dispensing powder coating material from a cardboard shipping box includes a long tube which is inserted into the shipping container and draws in the powder coating material from the bottom of the container. The container is further carried at an angle on a vibrating platform to agitate the material.
However, such a system is unsatisfactory because the tube must be disassembled and cleaned when it is desired to use a different color of powder coating material, thereby slowing the operator's progress. Additionally, the box and plastic liner must be opened to insert the tube, thereby subjecting the material to contamination as well as exposing the operator to the material. Moreover, the tube may be prone to clogging since a large amount of material may accumulate in the tube when the material is not being dispensed. Also, such tubes may have a double-walled design which can trap the material, thus leading to contamination when the tube is inserted in a another container with a different colored material. Furthermore, the tube may have a cap or other fluidizing parts which may fall off and get lost in the powder coating material. Gravity feed and fluid bed hoppers are also known, and have their own disadvantages
Accordingly, it would be desirable to provide an apparatus for dispensing powder coating material from a shipping container which does not suffer from the above disadvantages. In particular, the apparatus should allow the material to be dispensed without opening the lid of the box, i.e., breaking the factory seal. The apparatus should further allow the operator to easily and quickly switch to different colors and/or containers of powder coating material without cleaning or disassembling the apparatus. The apparatus should further be inexpensive to manufacture, and should not have any parts which are subject to fall off while submerged in the powder coating material. The apparatus should dispense as much of the material from the container as possible to prevent waste, but should also allow the operator to seal the container for later reuse. The present invention provides a nozzle apparatus for dispensing powder coating material having the above and other advantages.